Creating objects through functions - memory usage

Question

If I create custom objects through functions like this:

function createCustomObject ( state ) {
    let obj = { state };
    obj.doSomething = function ( ) {
        // do something
    };
    return obj;
}

let myNewObject = createCustomObject( { foo: 'bar' } );
myNewObject.doSomething();

How does that work out memory-wise? Does JavaScript keep a separate copy of the doSomething method for each of the objects I create? If I need to create thousands of objects will using prototypes/composition be more efficient?

It may be easier to see from a different viewpoint : http://stackoverflow.com/a/41416177/1636522. — , Jan 17 '17 at 06:01

score 0 · Accepted Answer · answered Jan 17 '17 at 05:36

Yes, a new object will be created for each call.

function createCustomObject ( state ) {
  let obj = { state };
  obj.doSomething = function() {};
  return obj;
}
var o1 = createCustomObject();
var o2 = createCustomObject();
console.log(o1 === o2); // false
console.log(o1.doSomething === o2.doSomething); // false

If you want to share the methods, yes, better use prototypical inheritance.

function CustomObject ( state ) {
  this.state = state;
}
CustomObject.prototype.doSomething = function() {};
var o1 = new CustomObject();
var o2 = new CustomObject();
console.log(o1 === o2); // false
console.log(o1.doSomething === o2.doSomething); // true

Creating objects through functions - memory usage

1 Answers1